The present invention relates to an indicator useful in testing the pulmonary function of a subject. The peak ventilatory flow rate of a subject is a good indication of overall pulmonary function. Peak expiratory flow rate is a widely recognized indication of pulmonary function with reference to certain lung conditions, such as asthma and emphysema. Persons not afflicted with such lung conditions can expel the air from the lungs much more rapidly than persons who are afflicted. Numerous devices for measuring the expiratory flow rate are provided. These devices are frequently expensive and complex.